1. Field of Invention
This invention relates to a one step process for achieving greatly improved magnetic recording disks with far superior wear resistance, magnetic performance, and surface finish.
2. Description of Prior Art
It is well known in the art to increase the durability of coatings by adding thereto particles of some type of extremely hard material such as Al.sub.2 O.sub.3. One example is the manufacture of magnetic recording disks employing a coating having magnetic particles and a small percentage of load bearing particles such as Al.sub.2 O.sub.3, typically larger in diameter than the final coating thickness. Such a magnetic disk customarily is made of a metallic substrate member (thickness.ltoreq.153 mils) such as an AlMg alloy on which a magnetic recording layer (thickness.ltoreq.1-1.5.mu.) is deposited. It is very difficult to design a wear resistant surface where the hard particles are planar to the surface. There are problems in getting a monodispersed powder, as well as tendencies for the resin binder to conform over the hard Al.sub.2 O.sub.3 particles.
After applying the magnetic coating layer containing the load bearing particles to the substrate and curing the coating, a buffing or polishing operation follows to ultrafinish the surface of the magnetic coating layer. Such buffing is time consuming, generates debris, and furthermore, removes almost 40% of the magnetic material from the recording layer, thereby reducing the effective magnetic properties of the finished recording layer. Also, some of the load bearing particles may be torn out of the coating during buffing, but some invariably end up protruding above the coating surface after polishing. This latter feature is thought to be highly desirable in protecting the magnetic coating from damage associated with contact with the head and corresponding loss of information.